Heritable Variation in a Polypeptide Subunit of the Major Storage Protein of the Bean, Phaseolus vulgaris L.

Abstract

Electrophoretic analysis of the major seed protein, G1 globulin, from four strains of Phaseolus vulgaris L. revealed a three-banded pattern for two strains having a high methionine content (BBL 240 and PI 302,542). The other two strains (PI 207,227 and PI 229,815) known to have a lower seed methionine content, had a two-banded subunit pattern for the G1 globulin. Analytical ultracentrifugation confirmed that globulin from the two-banded strains underwent pH-dependent reversible dissociation similar to that previously found for a three-banded cultivar; additionally, the protomer molecular weight showed that three subunits of about 50,000 molecular weight each were present in the G1 globulin of the two-banded strain. Gel patterns of G1 globulin from the two strains used as parents, BBL 240 and PI 229,815, showed differences in the largest subunit, which appeared as either a 53,000 molecular weight polypeptide known to be present in the three-banded strain, or as a shorter polypeptide having a molecular weight close to 47,000. Analysis of G1 protein from portions of single hybrid seeds showed a banding pattern intermediate between the two- and three-banded types. The subunit pattern from all seeds with intermediate-banded parents segregated in a manner consistent with that expected for control of the polypeptide by a single Mendelian gene. The remaining portions of the seeds were grown to confirm that they represented true crosses. The procedures used are essentially nondestructive, and can be used as a basis for selecting seeds having different protein characters.